High voltage transformer



Dec. 5, 1967 w. R. WELTY ETAL 3,356,931

HIGH VOLTAGE TRANSFORMER Filed Nov. 19, 1965 m fA/razx Mzz/A/uzhdar United States Patent 3,356,931 HIGH VOLTAGE TRANSFORMER William R. Welty, Fullerton, and Leo W. Wilson, Huntington Beach, "Calif, assignors to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Filed Nov. 19, 1965, Ser. No. 508,734 7 Claims. (Cl. 323-48) This invention relates to pulse-type transformers and more particularly to an apparatus including mutually coupled windings connected in a manner to achieve an extremely high voltage handling capability.

The conventional transformer is wound on a single core in a manner such that the full secondary voltage appears between windings as well as between core and secondary. In transformers with appreciable bandwidth and reasonable efiiciency, this type of fabrication is generally limited to a maximum safe voltage of a small fraction of a megavolt.

It is therefore an object of the present invention to provide an improved transformer configuration capable of producing a very high secondary voltage without breakdown.

Another object of the invention is to provide a transformer that is capable of producing very little phase or amplitude distortion over a very wide frequency range.

Still another object of the invention is to provide a transformer that may be designed to produce much larger secondary surge impedances than possible with conventional methods.

A further object of the invention is to provide a transformer that is of significant advantage in situations requiring the transformation of broad spectoral electrical wave functions to very high voltage amplitudes with a minimum of distortion. A still further object of the invention is to provide a transformer apparatus that has typical applications in a high voltage pulse modulator for klystrons, traveling wave tubes, X-ray tubes or gamma ray tubes.

'In accordance with the present invention, a series of individual transformers are interconnected in such a manner that the secondary voltage is divided equally between them. The individual cores of the respective transformers are both insulated from ground and connected to points of the apparatus having the most appropriate potential relative to the respective windings. The secondary to primary induced voltage ratio of each transformer is slightly greater than unity. The slight excess is to compensate for copper and coupling loss in the transformer windings and associated delay lines to leave an effective ratio of unity. In the apparatus of the invention, all the primary windings are'connected in series and all the secondaries are connected in series in the same order. In addition, delay lines are connected fromthe primary to the secondary windings in a manner to provide equal delay to the primary excitation waveform to enhance the high frequency response of the transformers.

The above-mentioned and other features and objects of this invention and the manner of obtaining them will be come more apparent by reference to the following description taken in conjunction with the accompanying drawing, wherein the figure illustrates a schematic circuit diagram of a preferred embodiment of the invention.

Referring now to the drawing, there is shown a schematic circuit diagram of the transformer apparatus of the present invention for providing an output voltage nE where n is a positive integer no less than two and E is the input voltage, i.e., n is ratio of secondary voltage to primary voltage. In particular, the apparatus of the invention includes transformers T T T T T and T,, Transformers T through T have primary windings 10, 11, 12, 13, 14, 15; secondary windings 20, 21, 22, 23, 24

and 25; and cores 30, 31, 32, 33, 34 and 35 respectively. A reference surge impedance Z, for the transformer apparatus is defined as the fined as 1201rNi w Z where 7r=3.1416, N=turns per unit length, t=thickness of insulation pad between primary and secondary windings of the respective transformers T through T and e=dielectric constant of the insulation pads. On this basis, the transformer T is designed to have a winding surge impedance equal to n- 1 the transformer T a winding surge impedance equal to Z n-2 the transformer T a winding surge impedance equal to Z n2 the transformer T a winding surge impedance equal to Z/3; the transformer T a winding surge impedance equal to Z/2; and the transformer T a winding surge impedance equal to Z.

The primary windings 10 to 15 and the secondary windings 20 to 25 of transformers T ings 1015 and 2025 of transformers T through T are all poled in the same direction and the cores 30, 35 are referred to an extremity of the primary windings 10 connected to an input terminal 40. As previously specified, the input impedance at the terminals 39, 40 is equal to Z/n. The remaining unconnected extremity of secondary Winding 25 of transformer T is connected to an output terminal 42. The surge impedance relative to ground at the output terminal 42 looking into the apparatus of the invention is equal to I12.

In addition to the above, the apparatus of the invention includes delay lines D D D D D,, and D,, corresponding respectively to transformers T T T T T and T Delay lines D through D are characterized in that they ideally possess the same delay as the respective corresponding transformer. Delay lines D through D,, include inductive impedances 50, 51, 52, 53, 54 and 55, each of which have an impedance equal to the reference surge impedance Z. The impedances 50 through 55 are capacitatively coupled to conductive members 60 to 65, respectively, ina manner to provide the aforementioned delays for delay lines D through D,, equal to that of the corresponding transformers T through T respectively. Conductive member 60 of delay line D is referenced to ground. The low tension extremity of secondary winding 20 of transformer T is connected through impedance element 50 of delay line D and through conductive member 61 of delay line D in the order named to the high tension extremity of priing 20 of transformer T of transformer T Similarly, the high tension extremity of secondary winding 20 of transformer T is connected through impedance element 51 of delay line D and through conductive member 62 of delay line D to the high tension extremity of primary winding 11 of transformer T the high tension extremity of secondary winding 21 of transformer T is connected through impedance element 52 of delay line D and through conductive member 63 of delay line D to the low tension extremity of primary winding 13 of transformer T the low tension extremity of secondary winding 23 of transformer T is connected through impedance element 53 of delay line D and through conductive member 64 of delay line D to the high tension side of primary winding 13 of transformer T the high tension extremity of secondary winding 23 of transformer T is connected through impedance element 54 of delay line D and through conductive member 65 of delay line D to the high tension extremity of primary winding 14 of transformer T and the high tension extremity of secondary winding 24 of transformer T is connected through impedance element 55 of delay line D to the high tension extremity of primary winding 15 of transformer T In order to optimize the high frequency response, the delay of the delay lines D through D,, should be the same as the delay of the corresponding transformer T through T Direct connections with no delay may be made if frequency response characteristics are not important.

In operation, a voltage E is applied across the input terminals 39, 40, the high side of the input voltage being applied to terminal 40. In that the delay through delay line D is the same as the delay through transformer T a voltage E appears at the high side of primary winding at the same time as the voltage flows throughthe wind- The surge impedance mary winding 10 between the windings 10,- 20 causes the voltage to double at the high side of secondary winding 20. Subsequent current flow through the primary winding 10 maintains this voltage relationship. In the same manner, the voltage wave front propagates through delay line D and transformer T and through delay line D and transformer T until the last transformer, T is reached. The hightension extremity of secondary winding 25 of transformer T,, produces an output voltage n-E where the input voltage applied to the input terminal 40 is E. I he apparatus is characterized by the fact that the respective cores 30 35 are connected individually to an extremity of one of the primary or secondary windings of the transformers T through T respectively. Thus, the voltage difference between any of the cores 30-35 and any part of the windings 10 through and through is never greater than B. This allows extremely high voltages'to be generated without the normal winding-fo-core breakdown limitation experienced inconventional transformers. In addition, the delay lines D through D enable the transformer apparatus -to operate under an extremely wide range of frequencies by causing the electrical impulses to propagate along both the primary and second- .ary windings at the same velocity.

Although the invention has been shown in connection with a vcertain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

What is claimed is:

1. A high. voltage transformer apparatus for generating an output voltage that is n times the amplitude of input voltage wherein n is no less than 3, said apparatus comprising first, second, third (11-13), (rt-2) and .(n-1) transformers of predetermined delay and each possessing primary and secondary windings mutually coupled with individual cores, each of said primary and secondary windings having first and second terminals, the direction of polarity between respective first and second terminals being consistent and the respective turns ratio of said primary and secondary windings being substantially unity; means for connecting said first terminals of said primary and secondary windings of said first, second and third (n2) transformers to said second terminals of said primary and secondary windings of said second, third (n-l) transformers, respectively; means for maintaining said second terminal of said primary winding of said first transformer at a reference potential level; and means connecting said respective second terminals of said secondary windings of said first, second, third (n2), and (.n-1) transformers to said respective first terminals of said primary windings thereof whereby a voltage relative to said reference potential level applied to said second terminal of said secondary winding of said first transformer is transformed to n times its amplitude at said first terminal of said secondary winding of said (n1) transformer.

2. The high voltage transformer apparatus as defined in claim 1 wherein said means connecting said respective second terminals of said secondary windings of said first, second, third (n-Z), and (nl) transformers to said respective first terminals of said primary windings thereof includes first, second, third (rt-2) and (rt-1) delay elements, respectively, each of said delay elements introducing a delay substantially equal to said predetermined delay. 7

3. The high voltage transformer apparatus as defined in claim 2 wherein said first, second, third (n-2), and (n--l) delay elements are referenced to said respective second terminals of said primary windings of said first, vsec ond,.third (n2) and (11-4) transformers.

4. The high voltage transformer apparatuses defined in claim 1 wherein a reference impedance, Z, is defined as the square root of the product of the input and output .impedances of said transformer apparatus and wherein the surge impedance of each of said first, second, third (rt-2), and n-1 delayelements is equal to said reference impedance, Z, and the winding surge impedances of said first, second, third (rt-2 (n- -l) transformers are equal to and Z, respectively.

5. The high voltage transformer apparatus as defined in claim ,1 wherein said individual cores of said first, second, third (r -2), (n-1) transformers are referencedto said respective rst terminals of said primary windings thereof. i l V 6. A high voltage transformer apparatus having an output voltage'that is n times the voltage applied thereto where n is an integer no less than three and wherein a reference impedance, Z is defined as the square root of the product of the input and output impedances, said transformer apparatus comprising first, second, third (n-3), (P1-2), (n-l) transformers of predetermined delay, each transformer possessing primary .and secondary windings of substantially unity turns ratio coupled with individual .cores and having first and second terminals, the direction of polarity between respective first and second terminals being uniformly in the same direction,

said first, second, third... (n3), (n2), (n1) transformers having winding surge impedances equal to .2 .2 n-dyrn-sym-a 32 and Z, respectively; means .for connecting said first terminals of said primary and secondary windings of said first, second, third (n-3), (rt-2) transformers to said second terminals of said primary and secondary windings of said second, third (it-3), (n2), (rt-1) transformers, respectively; means for maintaining said second terminal of said primary winding of said first transformer at a reference potential level; first, second, third (rt-3), (rt-2), (rt-1) delay lines each providing a delay equal to said predetermined delay and having a surge impedance equal to Z, said first, second, third (rt-3), (rt-2), (n-l) delay lines being referenced to said respective second terminals of said primary windings of said first, second, third (n3), (n2), (n1) transformers, respectively; and means for connecting said respective second terminals of said secondary windings of said first, second, third (It-3), (n-2), (n-l) transformers through said first, second, third (n3), (n-Z), (n--1) delay lines, respectively, to said first terminals of said primary windings of said first, second, third (rt-3), (n2), (n-l) transformers whereby a voltage relative to said reference potential level applied to said second terminal of second secondary winding of said first transformer is transformed to n times its am- 6 plitude relative to said reference potential level at said first terminal of said secondary winding of said (n-1) transformers.

7. The high voltage transformer apparatus as defined in claim 6 wherein said individual cores of said first, second, third (rt-3), (11-2), (21-1) transformers are referenced to the respective first terminals of said primary windings thereof thereby to minimize the maximum voltage stress in said transformer apparatus,

References Cited UNITED STATES PATENTS 1,853,764 4/1932 Fischer 323-48 3,013,259 12/1961 Bleam 333-29 X 3,018,431 1/1962 Goldstein 323-45 JOHN F. COUCH, Primary Examiner.

WARREN E. RAY, Assistant Examiner 

1. A HIGH VOLTAGE TRANSFORMER APPARATUS FOR GENERATING AN OUTPUT VOLTAGE THAT IS N TIMES THE AMPLITUDE OF INPUT VOLTAGE WHEREIN N IS NO LESS THAN 3, SAID APPARATUS COMPRISING FIRST, SECOND, THIRD... (N-3), (N-2) AND (N-1), TRANSFORMERS OF PREDETEMINED DELAY AND EACH POCESSING PRIMARY AND SECONDARY WINDINGS MUTUALLY COUPLED WITH INDIVIDUAL CORES, EACH OF SAID PRIMARY AND SECONDARY WINDINGS HAVING FIRST AND SECOND TERMINALS, THE DIRECTION OF POLARITY BETWEEN RESPECTIVE FIRST AND SECOND TERMINALS BEING CONSISTENT AND THE RESPECTIVE TURNS RATIO OF SAID PRIMARY AND SECONDARY WINDINGS BEING SUBSTANTIALLY UNITY; MEANS FOR CONNECTING SAID FIRST TERMINALS OF SAID PRIMARY AND SECONDARY WINDINGS OF SAID FIRST, SECOND AND THIRD ... (N-2) TRANSFORMERS TO SAID SECOND TERMINALS OF SAID PRIMARY AND SECONDARY WINDINGS OF SAID SECOND, THIRD ... (N-1) TRANSFORMERS, RESPECTIVELY; MEANS FOR MAINTAINING SAID SECOND TERMINAL OF SAID PRIMARY WINDING OF SAID FIRST TRANSFORMER AT A REFERENCE POTENTIAL LEVEL; MEANS CONNECTING SAID RESPECTIVE SECOND TERMINALS OF SAID SECONDARY WINDINGS OF SAID FIRST, SECOND, THIRD... (N-2), AND (N-1) TRANSFORMERS TO SAID RESPECTIVE FIRST TERMINALS OF SAID PRIMARY WINDINGS THEREOF WHEREBY A VOLTAGE RELATIVE TO SAID REFERENCE POTENTIAL LEVEL APPLIED TO SAID SECOND TERMINAL OF SAID SECONDARY WINDING OF SAID FIRST TRANSFORMER IS TRANSFORMED TO N TIMES ITS AMPLITUDE AT SAID FIRST TERMINAL OF SAID SECONDARY WINDING OF SAID (N-1) TRANSFORMER. 